In modern medical practice, virtually all surgical procedures require some form of aspiration. Surgical aspiration is generally required to remove fluids from the surgical site to maintain unobstructed visualization of the field. More recently, many surgical instruments and microsurgical devices employ aspiration to draw fluids and tissue into mechanically driven cutters which greatly increase the speed of tissue removal while reducing the effort required by the surgeon. Also, some surgical procedures, such as lipectomy and the like, rely solely on aspiration to remove certain tissue and deposit.
Generally speaking, the aspirate from most of these devices and procedures comprises a mixture of tissue, body fluids, and blood. Because of the presence of the blood component, the aspirate usually is dark red in appearance. It has been observed that the color of the aspirate gives no indication of the amount or relative fraction of the aspirate which constitutes bloos from the patient. Thus the appearance of the aspirate provides no information to the surgeon concerning how much blood has been aspirated from the patient, nor any indication when operative or post-operative transfusion is required. Generally the surgical team monitors the vital signs of the patient, and relies on tests such as complete blood count and hematocrit as well as the gross amount of aspirate to determine the advisability of transfusion. These factors may involve delays in time, or may be imprecise indicators of transfusion requirements.